Buggy code:
public class revertHashByPartition { private static final String EMPTY_STRING = "" ; private static final String NULL_STRING = null ; private static final Exception NULL_EXCEPTION = null ; private static final int DEFAULT_LENGTH = 1 ; private static final String DEFAULT_ROOT_FACTOR = "2" ; private static final String DEFAULT_STARTING_INDEX = "0" ; private static final String DEFAULT_ENDING_INDEX = "0" ; private static final String DEFAULT_PARTITION_SIZE = "0" ; private static final String DEFAULT_ALGORITHM_TYPE = "md5" ; public static void main ( String ... parameterList ) { } public static final void revertHashByPartition ( String hash , String dictionary , int length , String rootFactor , String startIndex , String endIndex , String size , String algorithmType , String separator ) throws Exception { String [ ] dictionaryList = dictionary . split ( separator ) ; int dictionaryListLength = dictionaryList . length ; String endingSequence = new String ( new char [ length ] ) . replace ( "" , dictionaryList [ ( dictionaryListLength - 1 ) ] ) ; BigDecimal totalSequenceCount = new BigDecimal ( convertToSequenceIndex . convertToSequenceIndex ( endingSequence , dictionary , separator ) . toString ( ) ) ; BigDecimal startingIndex = BigDecimal . ONE ; if ( ! ( startIndex . equals ( revertHashByPartition . DEFAULT_STARTING_INDEX ) ) ) { startingIndex = new BigDecimal ( startIndex ) ; } BigDecimal endingIndex = BigDecimal . ONE ; if ( ! ( endIndex . equals ( revertHashByPartition . DEFAULT_ENDING_INDEX ) ) ) { endingIndex = new BigDecimal ( endIndex ) ; <START_BUG> endingSequence = convertToSequence . convertToSequence ( endingIndex , dictionary , separator ) ; <END_BUG> totalSequenceCount = new BigDecimal ( convertToSequenceIndex . convertToSequenceIndex ( endingSequence , dictionary , separator ) . toString ( ) ) ; } if ( ( startingIndex . compareTo ( totalSequenceCount ) ) > 0 ) { Exception exception = new Exception ( "starting<seq2seq4repair_space>index<seq2seq4repair_space>is<seq2seq4repair_space>greater<seq2seq4repair_space>thant<seq2seq4repair_space>the<seq2seq4repair_space>total<seq2seq4repair_space>sequence<seq2seq4repair_space>count" ) ; System . err . print ( exception . getMessage ( ) ) ; return ; } BigDecimal partitionCount = calculatePartition . calculatePartition ( totalSequenceCount . toString ( ) , rootFactor ) ; BigDecimal partitionSize = totalSequenceCount . divide ( partitionCount , 0 , RoundingMode . FLOOR ) ; BigDecimal lastPartitionSize = totalSequenceCount . subtract ( partitionCount . subtract ( BigDecimal . ONE ) . multiply ( partitionSize ) ) ; if ( ! ( size . equals ( revertHashByPartition . DEFAULT_PARTITION_SIZE ) ) ) { partitionCount = calculatePartition . calculatePartition ( size , rootFactor ) ; partitionSize = new BigDecimal ( size ) . divide ( partitionCount , 0 , RoundingMode . FLOOR ) ; lastPartitionSize = new BigDecimal ( size ) . subtract ( partitionCount . subtract ( BigDecimal . ONE ) . multiply ( partitionSize ) ) ; } final revertHashByPartition . PartitionData partitionData = new revertHashByPartition . PartitionData ( hash , dictionary , dictionaryList , endingSequence , totalSequenceCount , startingIndex , partitionCount , partitionSize , lastPartitionSize , algorithmType , separator ) ; revertHashByPartition . Distributor distributor = new revertHashByPartition . Distributor ( partitionData ) { public void callback ( Exception exception , String revertedHash ) { synchronized ( partitionData ) { System . out . print ( revertedHash ) ; Thread executorEngine = null ; while ( ( partitionData . executorEngineList . size ( ) ) != 0 ) { executorEngine = partitionData . executorEngineList . pop ( ) ; if ( ( ! ( executorEngine . isInterrupted ( ) ) ) && ( executorEngine . isAlive ( ) ) ) { executorEngine . interrupt ( ) ; } if ( ( ! ( executorEngine . isInterrupted ( ) ) ) && ( executorEngine . isAlive ( ) ) ) { partitionData . executorEngineList . push ( executorEngine ) ; } } partitionData . notifyAll ( ) ; } } } ; Thread distributorEngine = new Thread ( distributor ) ; distributorEngine . start ( ) ; while ( distributorEngine . isAlive ( ) ) ; return ; } private static class Executor implements Runnable , revertHashByPartition . Callback { private volatile revertHashByPartition . PartitionData partitionData = null ; public Executor ( revertHashByPartition . PartitionData partitionData ) { } public void run ( ) { } public void callback ( Exception exception , String result ) { } public void callback ( Exception exception , Object result ) { } } private static class Distributor implements Runnable , revertHashByPartition . Callback { private static volatile revertHashByPartition . PartitionData partitionData = null ; public Distributor ( revertHashByPartition . PartitionData partitionData ) { } public void run ( ) { } public void callback ( Exception exception , String result ) { } public void callback ( Exception exception , Object result ) { } } private static interface Callback { public void callback ( Exception exception , String result ) { } public void callback ( Exception exception , Object result ) { } } private static final class PartitionData { public static volatile String hash = null ; public static volatile String dictionary = null ; public static volatile String [ ] dictionaryList = null ; public static volatile String endingSequence = null ; public static volatile BigDecimal totalSequenceCount = null ; public static volatile BigDecimal startingIndex = null ; public static volatile BigDecimal partitionCount = null ; public static volatile BigDecimal partitionSize = null ; public static volatile BigDecimal lastPartitionSize = null ; public static volatile String algorithmType = null ; public static volatile String separator = null ; public static volatile Stack < BigDecimal [ ] > rangeList = new Stack < > ( ) ; public static volatile Stack < String > resultList = new Stack < > ( ) ; public static volatile Stack < Thread > executorEngineList = new Stack < > ( ) ; public static volatile BigDecimal resultCount = BigDecimal . ZERO ; public static volatile boolean hasFinished = false ; public PartitionData ( ) { }

Fix:
endingSequence = convertToSequence . convertToSequence ( endingIndex . toString ( ) , dictionary , separator ) ;